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13th November 2016 4:15 pm

Building a Phonegap App With Laravel and Angular - Part 4

In this instalment we’ll return to the back end. What we’ve done so far is typical of the kind of proof of concept we might do for a client early on, before going back and implementing the full set of features later on. Now we’ll go back and start to improve on that rather quick-and-dirty API by making sure we follow a few best practices.

For those of you who want to follow the Laravel Phonegap tutorials, I’ve created a dedicated category here for those tutorials. This category include RSS and Atom feeds, so if you only want to read those posts, you can do so. I’ve also done the same for the Django tutorials.

The Repository pattern

One of the issues we currently have with our API is that we’re passing our Eloquent models into our controllers. This may not seem like a huge issue, but it means that our controllers are tightly coupled to the Eloquent ORM, so if we wanted to switch to another ORM, or to a completely different database such as MongoDB, we’d have to amend our controllers. That’s not good.

However, using the Repository pattern we can first of all define an interface for our repository, and then create a repository class that implements that interface. That way we can interact with the repository class in our controllers, rather than using Eloquent models directly. Then, if we want to switch databases, we merely amend the repository class to change the implementation of those methods, without having to touch our controllers. Also, it makes it much easier to test our controllers in isolation, because we can easily mock our repository class using Mockery and hard-code the response, so our tests won’t touch the database and will therefore run more quickly. We won’t touch on that this time, but it’s a very significant advantage.

If you haven’t used interfaces before in PHP, they aren’t that hard. They merely specify what methods an object implementing that method must have and what arguments they must accept, but do not specify the details of the implementation. This makes it easy to determine if a class implements an interface correctly, because it will throw an exception if it doesn’t.

Save this to app/Repositories/EloquentPetRepository.php. Note how the methods closely mirror the underlying Eloquent methods, but they don’t need to - you could change the underlying implementation of each method, but the repository would still work in exactly the same way.

To make this work, we need to make a few changes elsewhere. In composer.json, we need to add the new Repositories folder to our classmap:

Note how we’ve moved much of the logic for creating a user into the create() method, and we return the token, not the user model. This makes sense as right now we only ever want to get a token back when we create a user. Later that may change, but there’s nothing stopping us adding a new method to implement that behaviour alongside this.

Then we update app/Http/Controllers/UserController.php to use our repository:

Now that we’ve got our repositories in place, we’re no longer tightly coupled to Eloquent, and have a more flexible implementation which is easier to test.

Separating our models from our JSON with Fractal

Another problem with our API is that our representation of our data is tightly coupled to our underlying implementation of our models. We therefore can’t change our models without potentially changing the data returned by the API. We need to separate our representation of our data from our actual model so that we can more easily specify the exact data we want to return, regardless of the underlying database structure.

Fractal provides a presentation and transformation layer for complex data output, the like found in RESTful APIs, and works really well with JSON. Think of this as a view layer for your JSON/YAML/etc.

In other words, Fractal lets you specify the format your data will take in one place so that it’s easier to return that data in a desired format. We’ll use Fractal to specify how we want our API responses to be formatted.

The transform method specifies how we want to represent our objects with our API. We can return only those attributes we want to expose, and amend the structure as we see fit. We could easily represemt relations in whatever manner we see fit, whereas before we needed to amend our queries to return the data in the right format, which would potentially be cumbersome.

Note that by default, Fractal places our data inside a dedicated data namespace. This is good because it leaves a place for us to put metadata such as pagination links, but it does mean our controller test has been broken. Let’s fix it:

We’re also going to amend our test settings to use the array backend for the cache, as this does not require any external dependencies, but still allows us to tag our cache keys (I’ll cover that in a future instalment). Change the cache settings in phpunit.xml as follows:

At present our User controller doesn’t actually return anything, and the auth only ever returns the token, so it’s not worth while adding a transformer now.

Wrapping up

That ends this lesson. We haven’t added any functionality, but we have improved the design of our API, and we’re now ready to develop it further. As usual, the backend repository has been tagged as lesson-4.

Next time we’ll start adding the additional functionality we need to our API.